THE NATURAL HISTORY OF OSTEOPENIA IN GIRLS WITH RETT SYNDROME

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. ABSTRACT HYPOTHESIS The purpose of this study is to characterize the natural history of osteopenia in girls and women with Rett Syndrome (RS) relative to normative data and to determine if associations between bone demineralization and dietary, endocrine, or physical factors are present in these individuals. We hypothesize that: 1) the early profound losses of bone mineral content in RS girls persist into adulthood, 2) the reduction in BMC is associated with decreased ambulatory ability and increased fracture rate in RS girls and women, and 3) their reduced bone mineral content bears little relationship with dietary or endocrine factors. SPECIFIC AIMS The specific aims of this study include: 1) To determine if regional and total body bone mineral content (BMC), measured in terms of absolute values and z-scores, by dual-energy x-ray absorptiometry (DXA) is significantly lower throughout childhood and adulthood in RS girls and women than in healthy individuals, the latter based on age-, gender-, and race-specific normative data; 2) To determine if the deficits in BMC, measured as z-scores, of RS girls and women are associated positively with: a) a clinical history of bone fractures, based on previous history/x-ray documentation, b) diminished ambulatory ability, based on their ambulation score; and c) the presence of specific MECP2 mutations 3) To determine if the deficits in BMC, measured as z-scores, are associated positively with the following dietary or endocrine factors: + Reduced dietary calcium (Ca) and vitamin D intakes, measured by dietary recall + The use of anticonvulsants, determined by clinical history and confirmed by serum drug levels + The use of birth control pills/injections, as determined by clinical history + Reduced regional muscle (arm, thigh, calf) mass derived from body circumference and skinfold measurements using standard anthropometric techniques + Decreased serum Ca, phosphorus (P), ionized Ca, bone-specific alkaline phosphatase, [25-OH]vitamin D, [1,25-(OH)2]vitamin D, osteocalcin, leptin; or increased intact PTH, D-teleopeptide, urinary Ca/creatinine output